1. Field of the Invention
The present invention pertains to apparatus for gaining access to the interior of containers. More particularly, the present invention is related to holders for mounting equipment such as sensing or measuring devices within high pressure containers, and tools for inserting and retrieving such holders without exposing the interior of the container to the surrounding atmosphere. Such apparatus is particularly applicable to high pressure fluid pipelines whereby sensors, such as corrosion or scale testing coupons, may be inserted into the fluid flow and retrieved therefrom without shutting down the pipeline flow.
2. Description of the Prior Art
In various industrial settings, it is often necessary to test or sample material under pressure in a pipeline or other enclosure. Access to such material may conceivably be had by first relieving the pressure, or shutting down the flow in the pipeline. This may be a difficult or dangerous procedure, and will usually be expensive. Retrieval tools, or retractors, are known for inserting holders or other fittings through a hole, for example, in the side of a pipe member without the need for shutting down the high pressure pipeline flow. The retrieval tools are also used to withdraw the holders from the pipeline without losing pipeline pressure.
While the holder is in position extending into the interior of the pipeline, a seal is maintained between a fitting mounted on the pipeline and the holder, or equipment attached thereto. During the removal of the holder from the pipeline, continuous sealing to maintain the pipeline pressure must be carried out. The holder must be capable of being totally withdrawn from the pipeline to allow access to testing equipment mounted on the holder for insertion within the pipeline. Thus, the fitting secured to the pipeline must be provided with a valve or other closure device to seal off the pipeline in the absence of the holder.
According to some prior art practices, a valve such as a gate valve is permanently installed on a fitting attached to the pipeline to selectively open and close communication to the tap hole in the side of the pipe. To install a holder extending into the pipeline a retrieval tool is secured and sealed to the valve housing with the holder positioned within the retrieval tool. The valve is opened and the retrieval tool is operated to advance the holder through the valve passage toward the pipeline. The procedure is generally reversed to retrieve the holder from the pipeline.
One type of retrieval tool must remain sealed to the valve housing as long as the holder is in position extending into the pipeline. In such case, the integrity of the sealing of the pipeline pressure is maintained by seal members carried by the retrieval tool rather than the holder.
In another type of tool, the holder may be sealed to fittings attached to the pipeline, and the retrieval tool removed. However, movement of the holder toward or away from the pipeline in the latter case is effected by moving a rod, to which the holder is attached, through a packing gland. A pressure differential across the packing gland may result in unintended movement of the rod.
Advancement of the holder according to prior art apparatus is generally achieved by rotating a screw device to which the holder is attached. Such rotation makes difficult the use of a metal-to-metal seal between the holder and the pipeline fittings. Another disadvantage of such rotation of the holder is the difficulty in providing the exact alignment within the pipeline of the equipment mounted on the holder. For example, where material testing samples, or coupons, are being placed within a high pressure fluid flow, the effect on the testing material may be altered depending on the orientation of the coupon relative to the direction of fluid flow. Generally, where scaling effects are to be determined, the coupon which is laminar in shape is placed with a flat side perpendicular to the direction of flow. For corrosion testing, coupons are placed parallel to the flow direction. Where the holder is advanced solely by a screw action, the orientation of attached coupons will be determined by the final position of the holder relative to the pipeline fittings. Even where additional orientation adjustments to the holder and attached coupons may be made, such adjustments may be difficult and dangerous operations due to the high pressure within the pipeline. Furthermore, since the operator cannot see the coupon, he must depend on fiducial marks on the holder if exposed, or on the retrieval tool.
Another type combination retrieval tool and holder is known whereby the holder may be secured and sealed to a fitting on the pipeline without the need for a permanent valve installation. To insert or to remove the holder a valve is connected to the pipeline fitting, and the retrieval tool is sealed to the top of the valve housing. The valve is opened and the retrieval tool is operated to advance a rod through the valve passage to either insert or retrieve the holder. Again, advancement of the holder is effected by rotating the rod to which the holder is attached. Thus, as discussed hereinbefore, a metal-to-metal seal between the holder and the pipeline fitting is difficult to obtain. Also, the holder and attached coupons must be oriented after the holder is sealed to the pipeline fitting. In this particular type of tool, rotation of the rod to advance or retract the holder is effected by turning an exterior sleeve of the tool.
Gaining access to the interior of a high pressure pipeline may be dangerous, particularly where such procedure is carried out manually. Consequently, it is highly desirable that retrieval tools and holders be designed to maximize safety and ease of use. The uncertainty of the orientation of the equipment positioned within the pipeline may be removed by a holder which is automatically oriented as desired when finally positioned on the pipeline.
Copending United States Patent Application Ser. No. 1,224 filed Jan. 5, 1979 now U.S. Pat. No. 4,275,592 discloses an extractor tool and a holder which may be advanced or retracted by operation of a placement member within the extractor tool. Generally, translational movement and rotational movement may be imparted to the placement member independently by means of two gear boxes at the disposal of the operator. The extractor tool incorporates a valve through which the holder may be passed in either a retrieval or insertion operation. During retrieval, the holder may be withdrawn clear of the valve, and the extractor tool broken above the closed valve to allow access to the holder. The extractor tool may then be reassembled, the valve opened, and the holder returned through the valve to the pipeline.
The holder includes a drive screw which serves to anchor the holder to a landing nipple attached to the pipeline, and a seal section which provides sealing engagement between the holder and the landing nipple. A holder section, on which equipment such as coupons may be mounted, is connected to the seal section. The drive screw is joined to the seal section by a shoulder bolt which permits limited relative translational movement between the drive screw and the seal section, but allows rotational movement therebetween. A clutch is provided to lock the drive screw against rotational movement relative to the seal section. The seal section and/or the attached holder section is equipped with an anchoring or orientation device which engages the landing nipple when the seal section is positioned therein and oriented in a predetermined direction. The anchoring of the seal section against rotation relative to the landing nipple occurs automatically, and thus assures the preferred orientation of equipment attached to the holder. In two embodiments disclosed, the seal section orientation device operates by spring-biasing to engage a detent, or recess, in the interior wall of the landing nipple.
The landing nipple provides an annular, longitudinally extending sealing surface to receive a packing-type seal carried by the seal section. A second seal is provided by contact between complimentary frustoconical surfaces on the landing nipple and the seal section. The drive screw is anchored to the landing nipple by matching low pitch threads. As the drive screw is being rotated by means of the extractor tool to anchor the holder to the landing nipple, the clutch causes the seal section to rotate with the drive screw. When the seal section has been advanced sufficiently in the area of the landing nipple sealing surfaces, the seal section anchor device engages the detent or recess of the landing nipple and the clutch is overridden as the drive screw is further rotated. Thereafter, advancement of the drive screw along the landing nipple threads occurs with rotation of the drive screw but without further rotation of the seal section. The aforementioned metal-to-metal seal provided by the frustoconical surfaces of the landing nipple and the seal section is closed by the drive screw being tightened on the seal section by means of the landing nipple threads.